It is known to provide a hybrid electric vehicle (HEV) having an electric machine and an internal combustion engine (ICE) connected in parallel to a driveline of the vehicle.
The vehicle may be operated in an electric vehicle (EV) mode in which torque to the driveline is provided exclusively by the electric machine. Alternatively the vehicle may be operated in a parallel mode in which torque is provided to the driveline by the ICE and electric machine.
It is desirable to provide a HEV having improved drivability. It is also desirable to provide a HEV having improved noise, vibration and harshness (NVH) performance in respect of the transition from the EV mode to the parallel mode of operation.
That is, it is desirable to provide a HEV having improved smoothness in the transition from EV to parallel mode. Smoothness can be compromised by fluctuations in vehicle rate of acceleration and/or speed when the transition is made, such as jerk or the like. It is further desirable to provide a HEV operable to transition from the EV mode to the parallel mode in a reduced time period.